Endocrinology Practice Questions

Q: Wolf Chaikoff effect:

Iodine induced hypothyroidism. ***Iodine induced hypothyroidism*** - The **Wolf-Chaikoff effect** describes the phenomenon where a high concentration of **iodide** temporarily inhibits the synthesis and release of thyroid hormones. - This transient effect leads to a short period of **hypothyroidism** in response to excess iodine. *Iodine induced hyperthyroidism* - This describes **Jod-Basedow phenomenon**, which is distinct from the Wolf-Chaikoff effect. - **Jod-Basedow** occurs when iodine administration in an iodine-deficient individual or someone with pre-existing thyroid abnormalities leads to **hyperthyroidism**. *Drug induced hyperthyroidism* - This is a broad category referring to hyperthyroidism caused by various medications, such as **amiodarone**, but does not specifically define the Wolf-Chaikoff effect. - The Wolf-Chaikoff effect specifically relates to the direct inhibitory action of high **iodine** concentrations on the thyroid gland. *Thyrotoxicosis due to excessive amount of thyroid hormone ingestion* - This condition is known as **thyrotoxicosis factitia** or **exogenous thyrotoxicosis**. - It is distinct from the Wolf-Chaikoff effect, which involves the thyroid gland's self-regulatory response to **iodine** overload rather than external hormone intake.

Q: All of the following statements about insulin-like growth factor (IGF) are true, except which of the following?

Also known as somatomedin A. ***Also known as somatomedin A*** - This statement is **imprecise and potentially incorrect** when referring to IGF in general. - **IGF-1** (the predominant form) is known as **somatomedin C**, not somatomedin A. - **IGF-2** is known as somatomedin A, but IGF-2 is less physiologically significant in postnatal growth. - In standard physiological discussions, "IGF" typically refers to IGF-1, making this statement the exception (false/imprecise). *Secretion is stimulated by insulin* - This statement is **TRUE** - insulin does stimulate IGF-1 secretion. - While **growth hormone (GH)** is the primary stimulator of hepatic IGF-1 production, **insulin acts permissively and directly** to enable IGF-1 synthesis. - **Insulin deficiency** (e.g., Type 1 diabetes) results in **low IGF-1 levels** despite elevated GH, demonstrating insulin's essential role. - Insulin enhances GH receptor expression and directly stimulates IGF-1 gene transcription in hepatocytes. *Required for skeletal and cartilage growth* - This statement is **TRUE** - IGF-1 is crucial for **postnatal skeletal and cartilage growth**. - IGF-1 mediates most of **GH's growth-promoting effects** through its anabolic actions on bone and cartilage. - It promotes **chondrocyte proliferation and differentiation**, essential for linear bone growth. *Mainly secreted by the liver* - This statement is **TRUE** - the **liver produces approximately 75%** of circulating IGF-1. - Hepatic IGF-1 production occurs in response to **growth hormone stimulation** via the GH receptor. - While other tissues produce IGF-1 for local (paracrine) effects, the liver is responsible for most **endocrine IGF-1**.

Q: What is the primary function of the paraventricular and supraoptic nuclei?

Regulate water balance.. ***Regulate water balance*** - The **paraventricular** and **supraoptic nuclei** of the hypothalamus synthesize **antidiuretic hormone (ADH)**, also known as **vasopressin**. - ADH plays a crucial role in **regulating water balance** by increasing water reabsorption in the kidneys. - This is the **primary and most fundamental function** of these nuclei. *Destruction can lead to diabetes insipidus* - While this statement is factually true, it describes a **pathological consequence** rather than the primary function. - Destruction of these nuclei impairs ADH synthesis, resulting in **central diabetes insipidus** with polyuria and polydipsia. - However, the question asks for the primary function, not the consequence of destruction. *Are located in the anterior pituitary* - The **paraventricular** and **supraoptic nuclei** are located in the **hypothalamus**, not the anterior pituitary. - These nuclei synthesize hormones that are stored and released by the **posterior pituitary**. *All of the options* - This is incorrect because the anterior pituitary location statement is false. - Additionally, only one option represents the primary function being asked for in the question.

Q: In uncomplicated cases, cortisol levels typically return to normal within how many days after acute hemorrhage?

3 days. ***3 days*** - In uncomplicated cases of acute hemorrhage, the normal physiological response involves a rapid stress-induced rise in **cortisol**, which typically **returns to baseline within 3 days**. - This quick normalization reflects the body's efficient ability to restore **homeostasis** after a transient stressor. *2 weeks* - A two-week period for cortisol normalization is unusually long for an **uncomplicated acute hemorrhage**. - Such a prolonged elevation might suggest ongoing stress, a more severe or **complicated hemorrhage**, or a different underlying pathology affecting the **hypothalamic-pituitary-adrenal (HPA) axis**. *10 days* - A 10-day period is still longer than typically expected for **uncomplicated cases**, indicating a more sustained stress response than usual. - While stress can prolong cortisol elevation, for a simple acute hemorrhage, this duration would be uncommon without other complicating factors. *7 days* - While cortisol levels can remain elevated for several days after significant stress, in **uncomplicated acute hemorrhage**, a 7-day period for normalization would be on the longer side. - The initial surge usually subsides more quickly as the acute physiological stress resolves.

Q: Osteoclasts are inhibited by:

Calcitonin. ***Correct Option: Calcitonin*** - **Calcitonin** is a hormone primarily produced by the **C-cells of the thyroid gland** that acts to lower blood calcium levels. - It **directly inhibits the activity of osteoclasts**, the cells responsible for bone resorption. - This is the primary mechanism by which calcitonin reduces serum calcium levels. *Incorrect Option: 1,25-dihydroxycholecalciferol (Activated Vitamin D)* - **Activated vitamin D** (calcitriol) primarily promotes **calcium absorption** in the intestines and kidney. - While it can indirectly affect osteoclasts by increasing calcium availability, it does not directly inhibit their activity. - In fact, chronic high levels can promote bone resorption by stimulating osteoclast activity. *Incorrect Option: Tumor Necrosis Factor (TNF)* - **Tumor Necrosis Factor (TNF)** is a pro-inflammatory cytokine that **stimulates osteoclast activity** and bone resorption. - It plays a significant role in **inflammatory bone loss**, such as in rheumatoid arthritis. - TNF promotes, rather than inhibits, osteoclast function. *Incorrect Option: Parathyroid Hormone (PTH)* - **Parathyroid hormone (PTH)** primarily increases blood calcium levels by stimulating bone resorption through **activating osteoclasts**. - It also promotes **calcium reabsorption** in the kidneys and the conversion of vitamin D to its active form. - PTH has the opposite effect of calcitonin on osteoclasts.

Q: The hormone produced from the area marked in the provided image of the adrenal gland is:

Aldosterone. ***Aldosterone*** - The image likely points to the **zona glomerulosa** of the adrenal cortex, which is the outermost layer. - The **zona glomerulosa** is primarily responsible for the synthesis and secretion of **aldosterone**, a mineralocorticoid. *Cortisol* - **Cortisol** is produced in the **zona fasciculata**, the middle layer of the adrenal cortex. - It is a **glucocorticoid** involved in stress response and metabolism. *Epinephrine* - **Epinephrine** (adrenaline) is produced by the **adrenal medulla**, the central part of the adrenal gland. - The adrenal medulla is neural tissue and not part of the adrenal cortex layers. *Dehydroepiandrosterone (DHEA)* - **DHEA** is an androgen produced in the **zona reticularis**, the innermost layer of the adrenal cortex. - This layer is responsible for secreting **adrenal androgens**.

Q: Which of the following is NOT true about vasopressin?

It is structurally similar to insulin. ***It is structurally similar to insulin*** - **Vasopressin** (arginine vasopressin or ADH) is a **nonapeptide** (9 amino acids), whereas **insulin** is a larger protein composed of 51 amino acids in two chains. Their structures are distinct and not similar. - While both are peptide hormones, their primary amino acid sequences and overall three-dimensional structures differ significantly, leading to distinct receptor interactions and physiological roles. *It increases peripheral vascular resistance* - Vasopressin acts on **V1 receptors** located on vascular smooth muscle, causing **vasoconstriction**. - This vasoconstriction leads to an increase in **peripheral vascular resistance** and, consequently, an elevation in **blood pressure**. *It is released in response to increased plasma osmolality* - **Osmoreceptors** in the hypothalamus detect increased **plasma osmolality** (due to dehydration or high solute concentration). - This triggers the release of vasopressin from the **posterior pituitary**, promoting water reabsorption to dilute the plasma. *It acts on V2 receptors in renal collecting ducts* - Vasopressin binds to **V2 receptors** on the basolateral membrane of principal cells in the **renal collecting ducts**. - This binding leads to the insertion of **aquaporin-2 channels** into the apical membrane, increasing water permeability and reabsorption.

Question 1

Wolf Chaikoff effect:

Accepted Answer

Iodine induced hypothyroidism

Answer

Iodine induced hyperthyroidism

Answer

Drug induced hyperthyroidism

Answer

Thyrotoxicosis due to excessive amount of thyroid hormone ingestion

Question 2

All of the following statements about insulin-like growth factor (IGF) are true, except which of the following?

Accepted Answer

Also known as somatomedin A

Answer

Secretion is stimulated by insulin

Answer

Required for skeletal and cartilage growth

Answer

Mainly secreted by the liver

Question 3

What is the primary function of the paraventricular and supraoptic nuclei?

Accepted Answer

Regulate water balance.

Answer

All of the options.

Answer

Destruction can lead to diabetes insipidus.

Answer

Are located in the anterior pituitary.

Question 4

In uncomplicated cases, cortisol levels typically return to normal within how many days after acute hemorrhage?

Accepted Answer

3 days

Answer

2 weeks

Answer

10 days

Answer

7 days

Question 5

Osteoclasts are inhibited by:

Accepted Answer

Calcitonin

Answer

1,25-dihydroxycholecalciferol (Activated Vitamin D)

Answer

Tumor Necrosis Factor (TNF)

Answer

Parathyroid Hormone (PTH)

Question 6

The hormone produced from the area marked in the provided image of the adrenal gland is:

Accepted Answer

Aldosterone

Answer

Epinephrine

Answer

Cortisol

Answer

Dehydroepiandrosterone (DHEA)

Question 7

Which of the following is NOT true about vasopressin?

Accepted Answer

It is structurally similar to insulin

Answer

It is released in response to increased plasma osmolality

Answer

It increases peripheral vascular resistance

Answer

It acts on V2 receptors in renal collecting ducts

Question 8

Disruption of the hypothalamic-pituitary portal system will lead to

Accepted Answer

High circulating levels of PRL, low levels of LH and FSH, leading to ovarian atrophy.

Answer

Increased follicular development due to elevated circulating levels of PRL.

Answer

Ovulation with subsequent increase in circulating progesterone levels.

Answer

Increased FSH levels due to reduced ovarian inhibin levels.

Endocrinology — MCQs

Endocrinology — MCQs

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